Modern automobiles and trucks are provided with sensors and warning systems which monitor the working functions of the vehicle engine and apprise the operator of serious malfunction. A major operating parameter of an internal combustion engine is the pressure of the lubricating oil, and any disruption of the lubricating system pressure is usually signalled by a dashboard warning light.
In internal combustion engines which are air cooled, and which rely on the lubricating system both for cooling and lubrication, failure of the lubricating system is a catastrophic event. Should the oil pressure fall significantly, and the engine continues in operation, the engine will destroy itself in a matter of a few seconds. The main bearings of the crankshaft will erode, the cylinder walls may be scored, and the engine may seize.
It is an unfortunate yet commonplace aspect of human nature that a vehicle operator who is concentrating on driving may ignore a dashboard light and be totally unaware of an engine malfunction. Should the oil pressure fail at freeway cruising speeds, the driver will barely have time to stop the vehicle before the engine is damaged, even if he or she reacts immediately to the warning light. Clearly, a mere dashborad warning light system is insufficient.
The following United States Patents exemplify the state of the art in devices which react to stop engine operation in the event of oil pressure failure:
3,914,735, 3,116,729, 3,601,103, 2,771,068, 3,362,388, 2,445,625, 3,384,062, 2,191,216.
Of these patents, U.S. Pat. No. 2,191,216 relates most directly to the present invention, in that it shows the engine to idle in the event of oil pressure failure, and that it senses idle speed by the voltage generated by the engine generator. However, this prior art system utilizes a solenoid device which must continuously energized, unlike the present invention as detailed in the following.